Compositions and methods for refractory coatings with ester carriers

ABSTRACT

This technology relates to refractory coatings used in metal casting by the foundry industry. Refractory coatings are often used to coat foundry cores and molds for the purpose of improving the quality of castings formed in connection with the cores or molds, particularly at the surface of the casting. Whereas traditional coatings comprise water based solvents that require excessive drying times or HAPs that emit hazardous VOCs, preferred embodiments of the present invention comprise refractory coatings having VOC-exempt ester based solvents, such as a dimethyl carbonate (DMC). Other preferred embodiments of the present invention comprise methods for reduction of VOC content in a foundry article.

CROSS REFERENCE TO RELATED APPLICATIONS

This continuation application claims priority to, and the benefit of,U.S. patent application Ser. No. 17/127,340 filed Dec. 18, 2020, U.S.patent application Ser. No. 16/039,200 filed on Jul. 18, 2018, now U.S.Pat. No. 11,484,935, U.S. Provisional Patent Application Ser. No.62/557,291 filed on Sep. 12, 2017, and U.S. Provisional PatentApplication Ser. No. 62/534,082 filed on Jul. 18, 2017.

FIELD OF THE INVENTION

This technology relates to refractory coatings used in metal casting bythe foundry industry.

BACKGROUND OF THE INVENTION

In many respects, refractory coatings are like special paints used inmetal casting. Unlike conventional paints, however, refractory coatingscan withstand the high temperatures of molten metal and also act as abarrier between the molten metal and a mold into which the metal ispoured for casting.

Refractory coatings are generally comprised of a high temperaturemineral, or other substance that is resistant to heat, suspended in aliquid (solvent) carrier. The coating is applied to, for example, a sandmold or core surface prior to casting. The liquid carrier is removed byevaporation, while the layer of mineral is left behind to coat the moldsurface. This layer can help prevent penetration of molten metal intothe sand, prevent erosion of the sand, and otherwise improve the qualityof a casting surface.

Foundries typically employ either a water based or solvent basedcoating. Water requires energy and equipment intensive drying, but it isenvironmentally friendly. Solvent based coatings can be air dried in areduced amount of time or ignited for very short dry times. Currentsolvent based foundry refractory coatings comprise of isopropyl alcohol(“IPA”), ethanol, methanol, naphtha, etc. However, some of these solventbased systems comprise hazardous air pollutants (“HAPs”) and all of themcomprise volatile organic compounds (“VOCs”). IPA and ethanol are themost commonly used solvent carriers in refractory coatings of thefoundry industry. Such pollutants and volatile compounds are subject tointense regulation, and many foundries that use conventional solventbased coatings spend considerable time and resources permitting for theVOCs.

Some VOC-exempt solvents such as acetone have been used in the past.However, acetone's high evaporation rate increases usage, and the lowflash point introduces serious explosion and fire risks to the foundry.

Therefore, there is an unmet need in the prior art for a solvent basedrefractory coating for use in the foundry industry, wherein the coatingprovides suitable performance characteristics, but is much safer to useand does not require additional permitting or include restrictions thataccompany traditional solvent based coatings.

SUMMARY OF THE INVENTION

To meet the needs described above, the present invention provides apartial or full replacement of refractory coating solvents with estercarriers, such as dimethyl carbonate (“DMC”) or t-butyl acetate, to forma solvent based refractory coating with reduced or no reportable HAPs orVOCs.

In one preferred embodiment of the present invention, a refractorycoating (also known as mold wash, paint, or dressing) composition isprovided preferably comprising a liquid ester carrier, such as 100% DMC,a suspending agent, a binding agent, water, an additive, and aparticulate refractory filler blend.

In operation, it has been found that refractory coatings formed inaccordance with a preferred embodiment of the present inventioncomprising DMC achieved an approximately 50%-97% reduction in reportableVOC's as compared to conventional refractory coatings. Notably, 100% VOCexempt coatings are achievable in accordance with preferred embodimentsof the present invention, although some coatings formed as describedherein may include trace VOCs that are introduced to the composition bythe binding agent.

As described herein, the term “carrier solvent” may comprise one or moreester carriers or a combination of one or more ester carriers withnon-ester solvents.

Examples of additives are surface active agents, such as, wettingagents, defoamers, dispersants, and rheology modifiers.

A preferred embodiment of the present invention is:

-   -   a refractory coating composition for foundry use comprising:    -   a liquid carrier comprising an ester carrier, the ester carrier        being provided at approximately 25% to 100% by weight of the        liquid carrier and 20% to 80% by weight of the composition;    -   a suspending agent provided at 2% or less by weight of the        composition;    -   a binder provided at approximately 1.5% to 3% by weight of the        composition;    -   water provided at up to approximately 2% by weight of the        composition;    -   one or more additives provided at approximately 2% or less by        weight of the composition;    -   and a particulate refractory material provided at approximately        13 to 78.5% by weight of the composition.

An alternative preferred embodiment of the present invention is:

-   -   a method for reduction of the VOC content in a foundry article,        the method comprising the steps of:        -   forming a foundry article;        -   forming a refractory coating composition comprising a liquid            carrier having an ester carrier;        -   diluting the composition with a VOC-exempt solvent;        -   applying the composition to the foundry article;        -   drying the composition to remove the ester carrier;    -   wherein the composition comprises: the ester carrier being        provided at approximately 25% to 100% by weight of the liquid        carrier and approximately 20% to 80% by weight of the        composition; a suspending agent provided at up to approximately        2% by weight of the composition; a binder provided at        approximately 1.5% to 3% by weight of the composition; water        provided at up to approximately 2% by weight of the composition;        one or more additives provided at up to approximately 2% by        weight of the composition; and a particulate refractory material        provided at approximately 13 to 78.5% by weight of the        composition.

Another alternative preferred embodiment of the present invention is:

-   -   A method for reduction of VOC content in a foundry article, the        method comprising the steps of:    -   providing a refractory coating composition having a solvent        carrier that comprises VOCs; and    -   diluting the composition with a VOC-exempt solvent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphic representation of weight loss % over time in minutes(drying time) data produced from a refractory coating comprising anapproximately 25/75 DMC/IPA (1:3 ratio DMC:IPA) ester carrierformulation. As shown, the data was collected at room temperature(“RT”), 35 degrees Celsius, and 49 degrees Celsius.

FIG. 2 is a graphic representation of weight loss % over time in minutes(drying time) data produced from a refractory coating comprising anapproximately 50/50 DMC/IPA ester carrier formulation. As shown, thedata was collected at RT, 35 degrees Celsius, and 49 degrees Celsius.

FIG. 3 is a graphic representation of weight loss % over time in minutes(drying time) data produced from a refractory coating comprising anapproximately 75/25 DMC/IPA ester carrier formulation. As shown, thedata was collected at RT, 35 degrees Celsius, and 49 degrees Celsius.

FIG. 4 is a graphic representation of weight loss % over time in minutes(drying time) data produced from a refractory coating comprising anapproximately 100% DMC ester carrier formulation. As shown, the data wascollected at RT, 35 degrees Celsius, and 49 degrees Celsius.

FIG. 5 is a graphic representation of weight loss % over time in minutes(drying time) data produced from a refractory coating comprising anapproximately 100° A IPA carrier formulation. As shown, the data wascollected at RT, 35 degrees Celsius, and 49 degrees Celsius.

FIG. 6 is a graphic representation of weight loss % over time in minutes(drying time) data produced from a refractory coating comprising an SBDN1087 base formula and various carrier solvents comprising DMC and IPA.As shown, the data was collected at RT.

FIG. 7 is a graphic representation of weight loss % over time in minutes(drying time) data produced from a refractory coating comprising an SBDN1087 base formula and various carrier solvents comprising DMC and IPA.As shown, the data was collected at 35 degrees Celsius.

FIG. 8 is a graphic representation of weight loss % over time in minutes(drying time) data produced from a refractory coating comprising an SBDN1087 base formula and various carrier solvents comprising DMC and IPA.As shown, the data was collected at 49 degrees Celsius.

FIG. 9 is a graphic representation of weight loss % over time in minutes(drying time) data produced from a refractory coating comprising an SBDN1086 or 1087 base formula and a carrier solvent comprising approximately75/25 DMC/IPA. As shown, the data was collected at 49 degrees Celsius.

FIG. 10 is a graphic representation of weight loss % over time inminutes (drying time) data produced from a refractory coating comprisingan SBDN 1086 base formula and a carrier solvents comprisingapproximately 75/25 DMC/IPA. As shown, the data was collected at 35degrees Celsius and 49 degrees Celsius.

FIG. 11 is a graphic representation of weight loss % over time inminutes (drying time) data produced from a refractory coating comprisingan SBDN 1086 or 1087 base formula and a carrier solvent comprisingapproximately 75/25 DMC/IPA. As shown, the data was collected at 35degrees Celsius.

FIG. 12 is a graphic representation of weight loss % over time inminutes (drying time) data produced from a refractory coating comprisinga carrier solvent comprising approximately 75/25 DMC/IPA and various %wt binder.

FIG. 13 is a graphic representation of weight loss % over time inminutes (drying time) data produced from a refractory coating comprisinga carrier solvent comprising approximately 50/50 DMC/IPA and various %wt binder.

FIG. 14 is a graphic representation of weight loss % over time inminutes (drying time) data produced from refractory coatings comprisinga carrier solvent comprising either approximately 75/25 or approximately50/50 DMC/IPA and approximately 3% binder.

FIG. 15 is a graphic representation of weight loss % over time inminutes (drying time) data produced from refractory coatings comprisinga carrier solvent comprising either approximately 75/25 or approximately50/50 DMC/IPA and approximately 2.5% binder.

FIG. 16 is a graphic representation of weight loss % over time inminutes (drying time) data produced from refractory coatings comprisinga carrier solvent comprising either approximately 75/25 or approximately50/50 DMC/IPA and approximately 2% binder.

FIG. 17 is a graphic representation of weight loss % over time inminutes (drying time) data produced from refractory coatings comprisinga carrier solvent comprising either approximately 75/25 or approximately50/50 DMC/IPA and approximately 1.5% binder.

FIG. 18 is a graphic representation of weight loss % over time inminutes (drying time) data produced from refractory coatings comprisinga carrier solvent comprising approximately 100% DMC and approximately 2%binder.

FIG. 19 is a graphic representation of weight loss (drying time) dataproduced from refractory coatings comprising a carrier solventcomprising either approximately 75/25 DMC/IPA or approximately 100% DMCand approximately 2% binder.

DETAILED DESCRIPTION OF THE EMBODIMENTS

While the present invention may be susceptible to embodiment indifferent forms, there is described herein in detail, specific preferredembodiments with the understanding that the present disclosure is to beconsidered an exemplification of the principles of the invention, and isnot intended to limit the invention to that described herein.

A preferred embodiment of the present invention comprises a low toabsent VOC refractory coating having performance characteristics thatare comparable to conventional solvent-based coatings and a safetyprofile that is highly advantageous over known refractory coatings. Thepreferred embodiment comprises an ester carrier, such as dimethylcarbonate or t-butyl acetate, to form a solvent based refractory coatingcomposition.

In at least one preferred embodiment of the present invention, the estersolvent based refractory coating composition is formed as follows:

A refractory coating (also known as mold wash, paint, or dressing)composition provided in accordance with the present invention preferablycomprises a liquid ester carrier, a suspending agent, a binding agent,water, and a particulate refractory filler blend. The liquid estercarrier is preferably primarily an organic compound that is colorless,flammable, and exempt from the restrictions placed on most VOCs in theUnited States. The liquid ester carrier is preferably classified as acarbonate ester, with or without the presence of a secondary solvent.The suspending agent is preferably a fine-grained natural rock or soilmaterial that comprises one or more clay minerals with traces of metaloxides and organic matter. Examples of the suspending agent includepalygorskite, montmorillonite, and sepiolite. The binding agent ispreferably a copolymer having a chemical affinity to the liquid estercarrier in the presence or not of a secondary binding agent such as anatural rosin. The particulate refractory filler blend preferablycomprises a fine to medium size fraction, the blend preferably having anaverage particle size of approximately d<30 microns, wherein no morethan approximately 10% by weight or volume of the total particulaterefractory filler blend has a particle size of approximately d<2microns. Examples of the filler blend include zirconium silicate (alsoknown as zircon) and/or aluminum silicate, graphite, silica, magnesiumsilicates, and the like, including combinations or blends ofrefractories.

In a preferred embodiment of the present invention, the liquid estercarrier is dimethyl carbonate (“DMC”). DMC has a similar flash point toIPA, and as such the light-off/burn properties of DMC are similar toIPA. Additionally, the evaporation rate of DMC is much higher than IPAor ethanol. Therefore, the drying times of refractory coatingscomprising DMC are substantially less than traditional coatingscomprising IPA or ethanol. This represents a significant advantage overtraditional air dry applications.

Exemplary refractory coating compositions provided in accordance withthe present invention preferably comprise: (i) a carrier DMC atapproximately 25-100% wt of the carrier and IPA at approximately 0-75%wt of the carrier, wherein the carrier comprises approximately 20-80% wtof the coating composition; (ii) clays at approximately 2% wt maximum ofthe coating composition; (iii) a binder (i.e., a vinyl acetate and vinyllaurate copolymer in ethyl acetate, the copolymer provided atapproximately 50% by weight of the binder), at approximately 1.5-3.0% wtof the coating composition; (iv) water at approximately 0-2% wt of thecoating composition; (v) additives at approximately 0-2% wt of thecoating composition; and (vi) a particulate refractory blend atapproximately 13-78.5% wt of the coating composition.

It is contemplated that alternative liquid ester carriers may be used inrefractory coating compositions provided in accordance with the presentinvention, including: t-butyl acetate, ethyl acetate, n-butyl acetate,allyl hexanoate, benzyl acetate, butyl butyrate, ethyl butyrate, ethylbenzoate, ethyl hexanoate, ethyl isovalerate, ethyl lactate, isobutylacetate, isoamyl acetate, ethyl ethanoate, n-butyl oleate, 2-ethylhexylcaprate/caprylate, isopropyl myristate, methyl oleate, n-propyl acetate,2-ethylhexyl acetate, pentyl acetate, ethylene glycol diacetate (EGDA),2-ethylhexyl acetate, isobutyl isobutyrate (IBIB), and propyl acetate.

The aforementioned ester carriers may also be used as VOC-exemptsolvents for dilution of refractory coating compositions prior toapplication of the composition to a foundry article.

In another preferred embodiment of the present invention, the liquidester carrier is t-butyl acetate.

For example, an alternative refractory coating composition provided inaccordance with the present invention preferably comprises: (i) acarrier t-butyl acetate at approximately 52% wt of the carrier andIPA/Methanol/VM&P Naphtha at approximately 7.5% wt of the carrier; (ii)clays at approximately 1.7% wt maximum; (iii) a phenolic resin atapproximately 0.4% wt; (iv) water at approximately 0.9% wt; and (vi) azircon refractory blend at approximately 66% wt. Prior to application toa mold or core during production, this formulation is preferably dilutedwith t-butyl acetate to approximately 37% solids.

To form a refractory coating provided in accordance with the presentinvention, DMC, IPA, and water are first added to a mixing vessel atmedium shear. Then, attapulgite clay (also known as palygorskite) isadded and shear is increased to approximately 700 rpm for a bladediameter of 22 inches. The mixed materials form a gel afterapproximately 10 minutes of mixing. Refractory powders, such as a zirconblend, binder, additives, and remaining liquids if available are thenadded to the vessel and mixed together for approximately another 10minutes. Blade action is ceased and the product is inspected forconformity with suitable refractory coating parameters.

In a preferred embodiment of the present invention, a method of using arefractory coating as described herein and provided in accordance withthe present invention is as follows.

A refractory coating provided in accordance with the present inventionmay be applied to a foundry article, such as molds and cores, invariable ways due to variable substrates with which the coating is used,and also variable requirements of the user. The refractory coating ofthe present invention may be provided in a concentrated form. In allcases, the coating is applied to provide a protective barrier between aliquid metal and the mold or core.

Before application to the mold or core, the refractory coating ispreferably diluted with an appropriate VOC-exempt solvent until therequired application viscosity for the coating is achieved. Coatings ofthe present invention may also be applied absent any dilution, such asin a concentrated form, depending on the application and intended use ofthe coating. In a preferred embodiment of the present invention, thesolvent is a liquid ester carrier comprising DMC. Once at the desiredviscosity, the coating can be applied to the mold or core by severalmethods, including dip, spray, flood (flow coat), brush, swab, and mittapplication methods. Dip application includes an immersing of the moldor core into the coating. This application allows full contact of thecoating to all areas. Spray application is a blowing of the coatingthrough the air in the form of tiny drops to form a coating layer on thesurface of the mold or core. Flood application is a pumping of thecoating through a hose to splash or flood onto the mold or core. Theexcess coating is collected and run again through the pump. Brush, swab,and mitt applications all use a tool (such as a paint brush, horse hairswab, or cotton mitt) soaked in the coating and contacted with the moldor core to apply the coating. Although these are the primary methods ofapplying a coating to a mold or core in the foundry industry, theinvention is not limited to these applications, as will be appreciatedby one of ordinary skill in the art.

In all applications, the wet refractory coating provided in accordancewith the present invention is allowed to dry or ignited to remove theester carrier. It is important to fully remove the ester carrier fromthe coating layer. If residual ester carrier remains, the ester carriercan be a source of gas which can cause defects in the metal casting.

In production, it has been found that refractory coatings formed inaccordance with a preferred embodiment of the present inventioncomprising DMC achieved an approximately 50% -97% reduction inreportable VOC's as compared to conventional refractory coatings.

For example, a first production test includes a pouring of high alloyiron and high alloy steel castings with pouring weights of approximately2,000-11,800 lb. Castings were poured using a vacuum process where abaseline refractory coating is sprayed onto a vacuum process mold film.A baseline coating comprising an IPA carrier was compared to twoexperimental refractory coating formulations provided in accordance withthe present invention. The experiment coatings, Formula A and Formula B,both comprised an ester carrier and employed an approximately 1:1 ratioof DMC:IPA. The difference between Formula A and Formula B was thechoice of binder employed therein. Formula A used a natural Binder A,such as gum rosin, and Formula B used a synthetic Binder B, such asvinyl acetate copolymer. Spray application of the Formula A and FormulaB coatings was satisfactory as required thicknesses were developed. Drytimes for the Formula A and Formula B coatings averaged 2 minutes whilethe baseline IPA coating dried in an average of 3 minutes and 30seconds.

The molds were then filled with sand. The experimental formulas bothexhibited sufficient sand erosion resistance. Once the mold was strippedfrom the pattern, it was observed that the baseline (IPA carriercoating) and Formula A exhibited similar coating cracking, while FormulaB showed improved resistance to cracking of the coating layer. Per apractice appreciated by those of ordinary skill in the art, metal wasthen poured into the molds, the molds were allowed to cool, and castingswere shot blasted before review. Both experimental Formulas A and Bdisplayed acceptable casting performance. Moreover, both experimentalcoating displayed acceptable properties to produce a commercially viablecasting.

The advantages of the experimental Formula A and B coatings include, butare not limited to:

Formula A: Approximately a 50% reduction in reportable VOCs and reduceddrying time as compared to conventional refractory coatings.

Formula B: Approximately a 50% reduction in reportable VOCs, reduceddrying time, and improved resistance to coating layer cracking ascompared to conventional refractory coatings.

In a second production test, high alloy iron and high alloy steelcastings were poured with pouring weights of approximately 2,000-11,800lb. Castings were poured using the vacuum process where a refractorycoating is sprayed onto the vacuum process mold film. A baseline coatingcomprising an IPA carrier was compared to two experimental refractorycoating formulations provided in accordance with the present invention.An experimental formulation also formed in accordance with a preferredembodiment of the present invention, Formula C, was tested utilizing anester carrier. Formula C employed an approximately 100% DMC carrier withthe synthetic Binder B described above. Spray application of the FormulaC coating was satisfactory as required thicknesses were developed. Drytimes for Formula C averaged 1 minute and 30 seconds while the baselineIPA coating dried in an average of 3 minutes and 30 seconds.

The molds were then filled with sand. Formula C exhibited sufficientsand erosion resistance. Once the mold was stripped from the pattern, itwas observed that Formula C showed improved resistance to cracking ofthe refractory coating layer. Per a practice appreciated by those ofordinary skill in the art, metal was poured, the molds were allowed tocool, and castings were shot blasted before review. Formula C displayedacceptable casting performance. Moreover, Formula C displayed acceptableproperties to produce a commercially viable casting.

The advantages of the experimental Formula C coating include, but arenot limited to:

Formula C: An approximately 97+% reduction in reportable VOCs, reduceddrying time, and improved resistance to coating layer cracking ascompared to conventional refractory coatings.

In another preferred embodiment of the present invention, a refractorycoating was once again produced with a liquid ester carrier, asuspending agent, a binding agent, a dispersant, and a particulaterefractory filler blend. The liquid ester carrier in this embodiment isdimethyl carbonate. The suspending agent is preferably a nanoclay, andmore specifically an organo-modified clay. The nanoclay component ispreferably montmorillonite, a 2-to-1 layered smectite clay mineral witha platey structure, and a surface modified to become organophilic withincreased compatibility with the solvent of choice. The binding agent ispreferably a copolymer having a chemical affinity to the liquid estercarrier. The dispersant agent is preferably an aromatic-free solution ofa high molecular weight block copolymer with pigment affinic groups. Theparticulate refractory filler blend preferably comprises a fine tomedium size fraction, the blend preferably having a medium particle sizeof approximately d<30 microns, wherein no more than approximately 10% byweight or volume of the total particulate refractory filler blend has aparticle size of approximately d<2 microns.

Another exemplary refractory coating compositions provided in accordancewith the present invention preferably comprise: (i) a carrier DMC atapproximately 100% wt of the carrier, wherein the carrier comprisesapproximately 28.5-32.5% wt of the coating composition; (ii) organoclayat approximately 2% wt maximum; (iii) a binding agent, such as vinylacetate copolymer, at approximately 1.5-3.0% wt; (iv) a block copolymerdispersant with pigment affinic groups at approximately 0-0.5% wt; and(v) a zircon refractory blend at approximately 66% wt.

To produce a refractory coating provided in accordance with the presentinvention, DMC, is added to a mixing vessel at medium shear. Then, theclay is added and shear is increased to approximately 700 rpm for ablade diameter of 22 inches. The mixed materials form a gel afterapproximately 10 minutes of mixing. Refractory powder(s), binder, anddispersant are then added to the vessel and mixed together forapproximately another 10 minutes. Blade action is ceased and the productis inspected for conformity with suitable refractory coating parameters.

In another refractory coating composition formed in accordance with thepresent invention, Formula D was made comprising an approximately 100%DMC carrier and zircon refractory. In this example, the carrier ispreferably 36.2 wt of the composition. This coating was tested under EPAMethod 24 and found to have zero measurable VOCs with a <0.05% by weightdetection limit. In production, Formula D was used to spray green sandmolds in a high production foundry. The green sand molds are producedand require assembly within approximately 15 minutes to meet productionneeds. The Formula D coating is preferably completely dry beforeassembly to avoid gas related casting defects. Formula D is preferred inthis application because foundries typically cannot permit foradditional VOCs on such lines, so traditional solvent based options aredisadvantageous because they result in emission of VOCs. Water basedcoatings would fit within the permitted standards for VOC emission, butthese types of coatings will not dry within the required time beforeassembly (i.e., approximately 15 minutes or less). Although an acetonebased coating would fit both dry time and permitting parameters, the lowflash point deems this technology too much of a fire and explosion riskto utilize. VOC-exempt ester based coatings, such as Formula D, aretherefore preferred and meets all VOC-exempt emission requirements.Specifically, the DMC based Formula D met all requirements. Formula Dwas produced and diluted to spray application Baume with DMC. Mixingproperties were acceptable for this application. Spray applicationproperties were suitable for an even coat on the molds. Several largegray and ductile iron castings (500-5,000 lb.) were poured. Castingresults were substantially better than uncoated molds which resulted insignificantly lower cleaning times.

A conventional solvent based paste coating may also be diluted witht-butyl acetate to achieve a reduction in VOC emission from the coating.The coating was diluted to typical flood coating or dipping viscosity(properties below at Table 1) and applied to a core. Applicationproperties were acceptable for flood coating. Ignition properties weresufficient for drying without excessive heat to the core. Additionally,and importantly, VOC emissions were reduced as a result of the dilutionwith t-butyl acetate. It is contemplated that other esters have asimilar reduction of VOC emission.

TABLE 1 Viscosity, cP 500 SOLIDS % 40 BAUME, deg 37

1. A refractory coating composition for foundry use comprising: a liquidcarrier comprising an ester carrier, the ester carrier being provided atapproximately 25% to 100% by weight of the liquid carrier and 25% to32.5% by weight of the composition; a binder; water provided at up toapproximately 2% by weight of the composition; one or more additivesprovided at up to approximately 2% by weight of the composition; and aparticulate refractory material provided at approximately 13 to 78.5% byweight of the composition.
 2. The refractory coating composition ofclaim 1, wherein the binder is provided at approximately 0.4% to 3% byweight of the composition.
 3. The refractory coating composition ofclaim 1, wherein the ester carrier is t-butyl acetate.
 4. The refractorycoating composition of claim 1, wherein the ester carrier is a carbonateester.
 5. The refractory coating composition of claim 4, wherein thecarbonate ester is dimethyl carbonate.
 6. The refractory coatingcomposition of claim 5, further comprising a suspending agent providedat 2% or less by weight of the composition.
 7. The refractory coatingcomposition of claim 6, wherein the suspending agent is an organoclay,the binder is a copolymer, and the particulate refractory materialcomprises zircon, aluminum silicate, silica, alumina, or a combinationof the foregoing particulate refractory materials.
 8. The refractorycoating composition of claim 4, wherein the binder is a vinyl acetateand vinyl laurate copolymer provided at approximately 50% by weight ofthe binder.
 9. The refractory coating composition of claim 4, whereinthe additive is a wetting agent, defoamer, dispersant, or a rheologymodifier.
 10. The refractory coating composition of claim 4, wherein theparticulate refractory material is a zirconium silicate flour having anaverage particle size of approximately d<30 microns, and wherein nogreater than approximately 10% by weight or volume of the particulaterefractory material has a particle size of approximately d<2 microns.11. The refractory coating composition of claim 4, the liquid carrierfurther comprising a volatile organic carrier.
 12. The refractorycoating composition of claim 11, wherein the volatile organic carrier isisopropyl alcohol.
 13. The refractory coating composition of claim 4,wherein the binder is a natural rosin or a hydrocarbon resin.